Light Mixing Lenses And Systems

ABSTRACT

Lighting modules and lighting systems containing one or more lighting modules, and associated methods, are provided that receive light from one or more light sources for projecting it to a target surface, e.g., in a uniform, patterned, or other controlled manner. In various embodiments, the lighting modules and lighting systems can be used to mix the light generated by one or more sources.

RELATED APPLICATION

The present application claims priority to a provisional applicationhaving Ser. No. 61/582,083, entitled “Light Mixing Lenses and System,”which was filed on Dec. 30, 2011. This provisional application is hereinincorporated by reference in its entirety.

FIELD

The present patent application generally relates to lenses and lightingsystems, and more particularly to lenses and lighting systems for lightmixing and/or color mixing.

INTRODUCTION

Lenses and lighting systems for high-power light sources, such as lightemitting diodes, can have a wide variety of configurations. In manycases, a particular configuration can be characterized by theillumination pattern it produces, by the coherence, intensity,efficiency and uniformity of the light projected by it, and so on. Theapplication for which the lens and/or lighting system is designed maydemand a high level of performance in many of these areas.

Many applications call for the ability to mix light from multiplesources, e.g., sources producing light of different colors. Further,light mixing is also useful for systems with large light sources. Inboth cases, it is difficult to produce uniformly mixed light and reducesource imaging. To date, light-mixing systems have typically providedtextured surfaces to spread the light from a light source. Theefficiency and capabilities of such systems are limited and theirillumination characteristics are typically sub-par.

Accordingly, there is a need for improved light-mixing lenses andlighting systems.

SUMMARY

In accordance with one aspect, an optical device is provided thatincludes a light pipe having a proximal end adapted for optical couplingto a light source, e.g., a light emitting diode (LED), to receive aplurality of light rays therefrom and a distal end providing an outputsurface for the light rays. The light pipe can be configured to causemixing of the light rays via reflection at one or more lateral surfacesthereof as the light rays pass through the light pipe. The opticaldevice can include a lens optically coupled to the output surface toreceive light therefrom. In various aspects, the output surface cancomprise one or more surface features configured to modulate an outputof the light passing therethrough. For example, the output surface caninclude a texture. In some aspects, the surface features can comprise aplurality of microlenses such that light rays exiting the light pipeexit through the microlenses.

In some embodiments, the light source can include a plurality of lightemitting sources generating light at different colors. For example, thelight source can be two LEDs providing light at different colors

In some embodiments, the lens can be a zoom lens that can move axiallyrelative to an output surface of the light pipe to change, e.g., theangular spread of the beam. In some embodiments, rather than utilizing asingle zoom lens, a zoom lens system comprising two or more lenses, atleast one of which is axially movable relative to the output surface ofthe light pipe, is employed to change the divergence of the output beam,e.g., between a narrow-beam spread and a wide-beam spread. For example,the zoom lens system can include a lens providing a positive opticalpower and another providing a negative optical power. In someembodiments, a multi-lens zoom system can provide, in the wide-beamposition, an output beam exhibiting a divergence (e.g., as characterizedby full width at half maximum (FWHM) of the light intensity distributionin a plane perpendicular to the direction of propagation) in a range ofabout 20 degrees to about 80 degrees.

In some embodiments, the lateral surface(s) of the light pipe can beconfigured to cause total internal reflection of at least some of thelight rays incident thereon. In other embodiments, the lateralsurface(s) of the light pipe can be metalized to cause specularreflection of light rays incident thereon.

In various embodiments, the light pipe comprises an input surface at theproximal end for receiving said light rays from the light source. Insome aspects, the output surface has a greater cross-sectional area thansaid input surface. In one aspect, the light pipe has a longitudinaldimension that is at least 10 times greater than any linear dimension ofsaid input surface. In various aspects, the light pipe can have aparallelepiped shape characterized by said input surface, said outputsurface, and four lateral surfaces. In a related aspect, any two opposedlateral surfaces of the light pipe diverge in a direction from saidproximal end to said distal end. A draft angle associated with thedivergence of the opposed lateral surfaces can be in a range of about 0degree to about 20 degrees.

In some embodiments, the light pipe includes at least two portionshaving different cross-sectional shapes. For example, the light pipe caninclude a proximal portion (a portion proximate to the light source)having one cross-sectional shape (e.g., circular), an intermediateportion having a different cross-sectional shape (e.g., hexagonal) and adistal portion having yet another cross-sectional shape (e.g., square).

In some embodiments, the shape of the output surface of the light pipeis selected to impart a desired cross-sectional shape to the light beamexiting the light pipe. For example, in some embodiments, the outputsurface of the light pipe can have a generally square shape with roundedcorners. In other embodiments, the output surface of the light pipe canhave a hexagonal or an octagonal shape. In some embodiments, the shapeof the input surface of the light pipe is different that the shape ofits output surface. For example, the light pipe can include a squareinput surface and a hexagonal output surface.

In some embodiments, the optical system can include a light interfaceunit coupled to the proximal end of the light pipe for facilitating thedelivery of light from a light source to the light pipe. In some cases,the light interface unit can also provide some mixing of light. In someimplementations, the light interface unit is integrally formed with theremainder of the light pipe, e.g., the light interface unit can form theproximal portion of the light pipe. In some embodiments, the lightinterface unit can include a cavity, which can be formed by a curvedinput surface, for receiving light from a light source. The inputsurface receives the light and couples the light, e.g., via refraction,into the light interface unit. In some embodiments, the input surface isconfigured such that a substantial portion of the received light isredirected toward a peripheral surface of the light interface unit. Theperipheral surface can in turn reflect the light incident thereon, e.g.,via total internal reflection or specular reflection, to the light pipe(or in cases in which the light interface unit is formed integrally withthe light pipe to the remainder of the light pipe).

In some embodiments, the light interface unit and the light pipe can beformed as separate pieces that are optically coupled to one another,e.g., via an adhesive and/or mechanical couplings.

In some embodiments, the light pipe can include an input surface that isshaped to conform to the shape of an output surface of a light sourcethat is optically coupled thereto. For example, the light pipe caninclude a concave input surface that conforms to a convex surface of adome of an LED.

In some embodiments of the optical system, a baffle is coupled to thelens. For example, a baffle can be coupled to a zoom lens utilized inthe optical system so as to capture certain light rays, e.g., those raysexiting the light pipe that fail to strike the zoom lens when the zoomlens is moved away from the output surface of the light pipe to be atits distal location.

In some embodiments, the light pipe can be formed of polymethylmethacrylate (PMMA), polymethacrylmethylimid (PMMI), glass,polycarbonate, cyclic olefin copolymer, cyclic olefin polymer, silicone,or other suitable materials.

In some aspects, the optical device can include a holder providing ahousing for the light pipe. In some embodiments, the holder can includea plurality of legs for coupling to openings in a substrate, e.g., aprinted circuit board (PCB), on which a light source is mounted.

In a related aspect, an optical device is disclosed, which comprises alight pipe having a proximal end adapted for coupling to a light sourceto receive light therefrom and a distal end through which light exitsthe light pipe, said light pipe being configured to cause mixing of thelight via reflection at one or more lateral surfaces thereof as thelight propagates from its proximal end to its distal end. A lens, e.g.,a zoom lens, is optically coupled to the distal end of the light pipe toreceive at least a portion of the light exiting the light pipe, saidlens being configured to project the received light as an output beam.The lens comprises at least one surface exhibiting a plurality ofsurface modulations for modulating (adjusting) at least onecharacteristic of the output beam. For example, the surface modulationscan adjust a maximum divergence angle of the beam and/or the beam'scross-sectional shape. In some embodiments, the surface modulations caninclude at least two different types of modulations disposed on at leasttwo different portions of the lens surface. For example, the differentsurface modulations can include sinusoidal modulations at two differentfrequencies. In some implementations, the two types of surfacemodulations are employed to impart different maximum divergence anglesto the light exiting through different portions of the lens surface.

In some embodiments, the profile of the lens surface having surfacemodulations can be characterized as a combination of a base profile anda modulation profile, each of which can in turn be characterized by amathematical function exhibiting a continuous first derivative.

In a related aspect, an optical system is disclosed that comprises aplurality of light modules disposed adjacent to one another, each ofsaid light modules comprising: a light pipe for receiving light from alight source at a distal end thereof and guiding the received light atleast partially via reflections at its one or more peripheral surfacesto a distal end thereof through which light exits the light pipe, and alens for receiving at least a portion of the light exiting the lightpipe to form an output beam. The light modules are positioned andoriented relative to one another such that the output beam of eachmodule at least partially overlaps with the output beam of at leastanother module on a target surface so as to provide collectively adesired illumination pattern on that surface. For example, the outputbeam of each module can at least partially overlap with an output beamof at least another module at one or more spatial locations.

In some embodiments of the above optical system, at least two of saidlight modules include light pipes having different cross-sectionalshapes.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled person in the art will understand that the drawings,described below, are for illustration purposes only. The drawings arenot intended to limit the scope of the applicant's teachings in any way.Like numerals are utilized to designate similar features of variousembodiments.

FIG. 1A depicts a partial cross-sectional view of an exemplary lightingmodule in accord with various aspects of the applicant's teachings.

FIG. 1B schematically depicts a zoom lens system in an embodimentaccording to the teachings of the invention in a narrow-beam position,where the zoom lens system includes a positive and a negative lens.

FIG. 1C schematically depicts the zoom lens system of FIG. 1B in awide-beam position.

FIG. 1D schematically depicts a zoom lens comprising a single lens in anembodiment according to the teachings of the invention in a narrow-beamposition.

FIG. 1E schematically depicts the zoom lens of FIG. 1D is a wide-beamposition.

FIG. 2 depicts an exploded view of the exemplary lighting module of FIG.1A.

FIG. 3 depicts in detail a proximal end of the exemplary lighting moduleof FIG. 1A.

FIG. 4 depicts in detail a distal end of the exemplary lighting moduleof FIG. 1A.

FIG. 5A schematically depicts an exemplary embodiment of the outputsurface of the zoom lens of FIG. 1A.

FIG. 5B is a schematic top view of the output surface of a zoom lensaccording to an embodiment in which a central portion of the surfaceexhibits one type of surface modulation and a peripheral portion of theoutput surface exhibits a different type of surface modulation.

FIG. 6A schematically depicts an exemplary shape of an output surface ofa light pipe utilized in an embodiment of an optical system according tothe teachings of the invention,

FIG. 6B schematically depicts another exemplary shape of an outputsurface of a light pipe utilized in an embodiment of an optical systemaccording to the teachings of the invention.

FIG. 7 schematically depicts a light pipe according to an embodiment ofthe invention having a light interface unit at a proximal end thereof.

FIG. 8 schematically depicts a light pipe according to an embodiment ofthe invention having a concave input surface for receiving light from alight source.

FIG. 9 schematically depicts a light pipe according to an embodiment ofthe invention in which different portions exhibit differentcross-sectional shapes.

FIG. 10A schematically depicts an optical system according to anembodiment of the invention having a holder with two legs for couplingto a printed circuit board (PCB) on which a light source, e.g., an LED,is mounted.

FIG. 10B is a partial schematic view of the optical system of FIG. 10Adepicting the two legs of the holder.

FIG. 10C schematically depicts a PCB on which a light source is mounted,where the PCB includes two openings for receiving the tips of the legsof the holder of the optical system shown in FIGS. 10A and 10B.

FIG. 11A is a partial schematic view of an optical system according toan embodiment of the invention which includes a zoom lens coupled to abaffle with the zoom lens positioned at a distal location relative to anoutput surface of the light pipe.

FIG. 11B is a schematic view of the optical system of FIG. 11A in whichthe zoom lens is positioned at a proximal location relative to theoutput surface of the light pipe.

FIG. 12 depicts in detail an exemplary lighting system incorporatingmultiple exemplary lighting modules of FIG. 1A.

DETAILED DESCRIPTION

The present application discloses, among other things, lighting modulesand lighting systems containing one or more lighting modules, andassociated methods, that receive light from one or more light sourcesfor projecting it onto a target surface, e.g., in a uniform, patterned,or other controlled manner. In various embodiments, the lighting modulesand lighting systems can be used to mix the light generated by one ormore sources. By way of example, the projected light can be homogenizedso as to create an output distribution of substantially uniformluminosity. In many cases, two or more light sources can be used togenerate light of different wavelengths. In various embodiments, thelighting modules and systems can be effective to mix the light ofdifferent colors. Further, in some embodiments, the lighting systems ofthe invention can be utilized for effective mixing of light generated byspatially separate individual sources of single color that collectivelymake up a single large source of light.

The devices and methods disclosed herein can be used with a wide varietyof light sources, including light-emitting-diodes and incandescentbulbs, or other coherent or non-coherent sources. Such devices andmethods can have a wide range of applications, including, for example,in spot lighting, customizable/adjustable lighting systems, householdlighting, flashlights, wearable headlamps or other body-mountedlighting, among others.

Throughout this application, the term “e.g.” will be used as anabbreviation of the non-limiting term “for example.” It should beunderstood that regardless of whether explicitly stated or not, allcharacteristics of the lighting modules and lighting systems describedherein are by way of example only, and not necessarily requirements. AllFigures merely depict exemplary embodiments of lighting modules and/orsystems that incorporate various aspects of the applicants' teachings.Further, the features of one embodiment can be combined with those ofany other embodiment.

With reference now to FIG. 1A, one exemplary embodiment of an opticalsystem (herein also referred to as a lighting module) 100 in accord withthe applicants' teachings is depicted. As shown in FIG. 1A, the lightingmodule 100 can include one or more light source(s) 110, a light pipe130, and a holder 120. Additionally, the lighting module can beassociated with a zoom lens 140 that can selectively focus the lightexiting the light pipe 130, as discussed in detail below.

Although any number of light sources can be employed in the lightingmodule 100, FIG. 1A depicts a single light source 110 being associatedwith the lighting module 100. Though in the exemplary embodimentdepicted in FIG. 1A the light source 110 is depicted as a single LEDchip having a substantially flat output surface, a person skilled in theart will appreciate that any number of a wide variety of light sources,including flat and domed light-emitting diodes, incandescent bulbs, orother coherent or non-coherent sources can be used with the systems andmethods described herein. Such systems and methods can have a wide rangeof applications, including, for example, in spot lighting,customizable/adjustable lighting systems, household lighting,flashlights, wearable headlamps or other body-mounted lighting, amongothers. Further, as will be discussed below, one or more light sourcescan be associated with each of the lighting modules. By way of example,the lighting module 100 can be configured to project the light from twoor more light sources 110 emitting light at the same or differentwavelengths. As will be otherwise discussed herein, the lighting module100 can be effective to mix the light of the two or more light sources.

The light pipe 130 can have a variety of configurations but is generallyconfigured to receive the light generated by the light source 110 andoutput the light towards the target surface. In the exemplary embodimentdepicted in FIG. 1A, for example, the light pipe 130 can include aproximal surface 132, a distal surface 136, and one or more lateralsurfaces (e.g., sidewalls 134) extending therebetween. Generallyspeaking, in this embodiment, the proximal surface 132 can receive lightfrom the light source 110 and act as an input surface for coupling thelight from the light source 110 into the light pipe 130. In variousembodiments, as the light from the light source 110 enters the lightpipe 130, the light from the light source 110 can be refracted towardsthe sidewall(s) 134. The term “refraction” is meant to indicate that thelight rays change direction, as can occur, for example, when they travelfrom one medium (e.g., air outside the light pipe 130) to another (e.g.,the material making up the light pipe 130). As one skilled in the artwill appreciate, some light generated by the light source 110 can enterthe light pipe 130 without refraction, for example, if the light strikesthe input surface 132 in a direction normal to the input surface 132.

After entering the light pipe 130, the light can be transmittedtherethrough toward the distal surface 136. The light can be transmitteddirectly through the light pipe 130 from the input surface 132 to theoutput surface 136 or indirectly via one or more reflections from thesidewall(s) 134. The sidewall(s) 134 can be adapted to reflect lightincident thereon via a wide range of mechanisms, for example via totalinternal reflection or via specular reflection, such as can be achievedby forming a metallic coating thereon. The reflected light can travel tothe distal surface 136, through which light can be coupled out of thelight pipe 130 (e.g., via refraction).

Though the input surface 132 is shown as a substantially flat surfacedisposed in a facing relationship with the exemplary LED chip, it shouldbe appreciated that the proximal surface 132 of the light pipe 130 canhave a variety of shapes and/or surface profiles for coupling lightgenerated by a source into the light pipe 130. For example, the surfacecan be shaped so as to avoid or reduce the passage of light through thelight pipe 130 without at least one reflection from the sidewalls 134and/or to avoid or reduce imaging the light source 110 in the projectedlight. In some embodiments, for example, the proximal input surface canbe configured to receive a light source. By way of example, the inputsurface 132 can be substantially concave so as to define a cavity inwhich a light source can be disposed.

As will be appreciated by a person skilled in the art, the outputsurface 136 of the light pipe 130 can also have a variety ofconfigurations. As shown in FIG. 4, for example, the distal surface 136can comprise surface features (e.g., texturing) formed thereonconfigured to further spread and or mix the light incident thereon inorder to alter the output beam characteristics. For example, in thedepicted exemplary embodiment, the distal surface can include an arrayof microlenses 138, each of which can be effective to focus, diverge, ordiffract light incident thereon out of the light pipe 130. In variousembodiments, the array of microlenses 138 can be effective to alter thedistribution of light relative to a substantially flat output surface,for example, without substantially increasing the maximum divergence oflight out of the light pipe 130.

The microlenses 138 can have a variety of shapes and/or sizes. Forexample, each microlens 138 can be dimensioned such that it is at leastabout 10 times smaller than the surface area of the output surface 136.As will be appreciated by a person skilled in the art, other structuresfor spreading or mixing the light at the distal surface 136 can also beemployed as part of or in place of the array of microlenses 138. By wayof example, surface texturing (e.g., texturing created in the die-moldor using chemical or mechanical etching or roughening) can be used onthe distal surface 136 as dictated by the desired output pattern and/orcharacteristics.

The size and the shape of the light pipe can also vary and can beselected so as to optimize the mixing of light. As best shown in FIG. 2,an exemplary light pipe 130 can be a substantially elongate member, forexample, having a length that is substantially greater than its width.By way of example, the length of the light pipe 130 can be at least 10times the width of the proximal surface.

The light pipe 130 can additionally have any number of sidewalls and canhave a variety of cross-sectional shapes. By way of non-limitingexample, the cross-section of the light pipe 130 can be square,circular, elliptical, hexagonal, star-shaped, etc. In variousembodiments, the shape and/or number of the sidewalls can be selectedbased at least in part, for example, on the input surface 132 of thelight pipe 130. By way of example, in a light pipe in which the inputsurface 132 forms a semi-hemispherical cavity in which the light iscoupled from the source 130 (e.g., a domed LED), the light pipe 130 canbe selected to have a circular cross-sectional shape (i.e., onesidewall). Alternatively, for example, a flat input surface 132 may lenditself to a square and or rectangular cross-section to improve themixing of light within the light pipe 130.

Moreover, each cross-section along the length of the light pipe can beof the same shape but have different dimensions. For example, in thedepicted embodiment, the cross-sectional area of the light pipe 130adjacent the proximal surface 132 can be smaller than thecross-sectional area of the light pipe 130 adjacent to the distalsurface 136.

With specific reference to the exemplary embodiment depicted in FIGS.1A-5B, for example, the light pipe includes four sidewalls of equallinear dimensions such that the light pipe 130 has a squarecross-section along its entire length. Moreover, the dimensions of theproximal end 132 can be smaller than the dimensions of the distal end136 such that the light pipe 130 is shaped as an inverted frustum. Oneof skilled in the art will appreciate based on the teachings herein, forexample, that the relative divergence of one sidewall relative to theopposed sidewall, for example, can be varied so as to alter the outputlight distribution. By way of example, a light pipe 130 configured suchthat the sidewalls 134 diverge along the length of the light pipe fromthe proximal surface 132 to the distal surface 136 can have a smalleroutput beam angle (as characterized by full width at half maximum (FWHM)of the light intensity distribution in a plane perpendicular to thedirection of propagation) than the output beam angle FWHM of a lightpipe in which the sidewalls 134 converge towards the distal surface 136.A draft angle associated with the divergence of the opposed sidewallscan be, for example, in a range of about 0 degree to about 20 degrees.

As noted above, the lighting module 100 can additionally include aholder 120. The holder 120 can have a variety of configurations butgenerally defines a bore 122 in which the light pipe 130 can bedisposed. In various embodiments, the bore 122 can have across-sectional area that is generally configured to match that of thelight pipe 130. Accordingly, the light pipe 130 can be inserted into theholder 120 and can be retained therein, at least partially, for example,by way of a frictional fit between the holder 120 and the light pipe130.

In various embodiments, the holder 120 can also be configured to seatthe light source 110. With reference now to FIG. 3, the proximal end 124of the holder 120 can contain a cavity in which the light source can bedisposed. By way of example, the holder can include a shoulder 126 whichcan abut at least a portion of the light source 110. Moreover, theshoulder 126 can include one or more vents 128 that allows for thedissipation of heat from the light source 110.

Accordingly, as shown in FIG. 3, for example, a light source can besecured within the proximal end 124 of the holder 120 with the lightpipe 130 disposed within the bore 122 of the holder 120. The holder 120can thus be configured to align the input surface 132 of the light pipe130 and the source 110 to efficiently couple light generated by thesource 110 into the light pipe 130. Moreover, a gap (e.g., an air gap)between the light source 110 and the input surface 132 of the light pipe130 can be in fluid communication with the vents 128 so as to preventoverheating of the source 110.

The holder 120 can additionally include one or more coupling mechanismsto enable the holder 120 to couple to adjacent lighting modules 100, aswill be discussed in detail below. With reference now to FIG. 4, theholder 120 can include, for example, a distal flange 123 having a bore125 formed therethrough. As will be appreciated by a person skilled inthe art, the bore 125 can enable coupling between adjacent lightingmodule(s) 100. By way of non-limiting example, a pin can be insertedthrough the bores 125 of adjacent lighting modules to movably or fixedlycouple the lighting modules 100. Moreover, the distal end of the holder120 can be configured to retain the light pipe 120 within the bore. Byway of example, the distal end of the holder can include one or moretabs 127 that can prevent the light pipe 120 from moving distallyrelative to the holder 130.

With reference again to FIG. 1A, the lighting module 100 can also beassociated with a zoom lens 140 disposed distal to the output surface136 of the light pipe 130 to receive light that is coupled out of thelight pipe 130 and direct it towards a target surface. In variousembodiments, the zoom lens 140 can be moved axially relative to theoutput surface 136 to alter the focusing power of the light beingdirected therethrough. By way of example, the zoom lens 140 can betranslated along the central axis of the light pipe 130 so as to varyits distance from the output surface 136 of the light pipe 130, therebyvarying the width (i.e. the convergence-divergence) of the output lightdistribution with respect to the central axis of the light pipe 130. Insome embodiments, for example, the zoom lens 140 can be moveable betweena position near the output surface 136 to a distal position at the focallength of the output surface 136. In such an embodiment, axial movementof the lens toward the holder 120 (e.g., to the wide zoom position 140a) can be effective to increase the width of the beam distribution onthe target surface whereas movement of the lens away from the holder 120(e.g., to the narrow zoom position 140 b) can decrease the width of thebeam distribution on the target surface.

As will be appreciated by a person skilled in the art, the zoom lens 140can be movable relative to the holder 120 using a variety of mechanisms.By way of example, the zoom lens 140 can be movable relative to theholder 120 and/or light pipe 130 via a step motor that can be controlledto position the zoom lens 140 at a desired location relative to theoutput surface 136 of the light pipe 130. As will be appreciated by aperson skilled in the art, in lighting systems in which multiplelighting modules 100 are associated, a zoom lens 140 associated witheach light pipe 130 can be moved individually relative to its respectiveholder 120 or in tandem with the other zoom lenses in the system.Alternatively, for example, the zoom lens 140 can be rotated within ahousing in a first direction (e.g., clockwise) to move the zoom lens 140away from the output surface 132 and in a second direction (e.g.,counterclockwise) to move the zoom lens 140 toward the output surface132.

As will be appreciated by a person skilled in the art, the zoom lens 140can be shaped so as to provide a desired final output distribution onthe target surface. As shown in FIG. 1A, for example, the zoom lens 140can include an input surface 142, a lens body 144, and an output surface146. The input surface 142 can be disposed in a facing relationship withthe output surface 136 of the light pipe 130 and can be configured tocouple the light received therefrom into the lens body 144, for example,via refraction as otherwise discussed herein. Light can traverse thelens body 144 and can exit through the output surface 146 of the zoomlens 140.

In some embodiments, rather than utilizing a single lens, the zoom lens(herein also referred to as the zoom lens system) can include aplurality of lenses, at least one of which is axially movable relativeto the output surface of the light pipe. For example, FIGS. 1B and 1Cschematically depicts a zoom lens system 10 (herein also referred to asa doublet zoom) that includes a lens 12 providing a positive opticalpower and a lens 14 providing a negative optical power. As least one ofthe lenses, and in some cases both, is axially movable relative to theoutput surface of the light pipe to change the angular spread of theoutput beam between a narrow-beam spread (shown in FIG. 1B) and awide-beam spread (shown in FIG. 1C). The use of a doublet lens systemwith one positive lens and one negative lens can be advantageous inapplications where a wide beam range, e.g., a divergence (FWHM) in arange of about 20 to about 80 degrees, is required. In embodiments inwhich the zoom lens includes a single positive lens (herein alsoreferred to as a singlet zoom), in the “intrafocal position” (i.e., whenthe lens is placed close to the output surface of the light pipe), thepositive power of the lens can reduce the divergence of the beam exitingthrough the output surface of the light pipe (See FIGS. 1D and 1E forschematic representation of a narrow-beam and wide-beam spread of theoutput beam in a system in which a singlet zoom 16 is employed). Incontrast, the positive and the negative optical powers of the lenses ofa doublet zoom allow achieving much wider beam spread, e.g., in a rangeof about 20 degrees to about 80 degrees (FWHM), when zoom system is inthe “intrafocal position.” Further, in many applications, amultiple-lens zoom lens system can provide other advantages, such asconventional advantages known in the art.

As will be appreciated by a person skilled in the art, the input surface142 and output surface 146 of the zoom lens 140 can be configured tocontrol the final output beam characteristics. By way of example, theoutput surface 146 can include surface features formed thereon that canprovide additional control over the cross-sectional shape and/or themaximum divergence angle of the output beam and/or its “texture” on atarget surface. For example, the output surface 146 can be configured tofurther mix the light such that the final output beam can have across-sectional shape that differs from the light received at the inputsurface 142. Although a beam of light emitted from a light pipe having asquare cross-section can be similarly shaped (i.e., substantiallysquare), the output surface 146 of the zoom lens 140 can be configuredto mix the light, for example, so as to reduce the sharpness of theedges of the projected light pattern. By way of example, the outputsurface 146 of the zoom lens 140 can comprise surface features (e.g.,annular rings, perturbations, microlenses) that are configured tomodulate the output light distribution in a controlled manner.

For example, with reference now to FIG. 5A, a pattern of sinusoidalgrooves can be formed in the output surface 146 of the zoom lens 140.The sinusoidal grooves can have a variety of configurations. By way ofexample, the tangent of the sinusoidal grooves at one or more pointsalong the surface can deviate less than about ±5 degrees relative to thetangent of a nominal surface 148 in which the grooves are formed atthose points as depicted in FIG. 5A. In various embodiments, thesinusoidal grooves can be effective to scatter and/or modulate the lightoutput from the light pipe 130 to decrease the sharpness of the edges ofthe output light distribution (e.g., reduce the appearance of a squareoutput pattern on a target surface) and/or modulate the maximumdivergence of the output light beam. By way of example, the sinusoidalgrooves can reduce, or eliminate, high frequency components in a Fouriertransform of the cross sectional intensity of the output lightdistribution. It should be understood that the controlled modulation ofthe output surface 146 can be achieved by employing patterns other thansinusoidal. Further, such controlled modulation can be implemented oneither surface, or both surfaces, of the zoom lens. Yet, in otherembodiments, rather than, or in addition to, imparting controlledmodulation to one or more surfaces of the zoom lens, one or moreadditional optical elements (e.g., lenses) having at least a surfaceexhibiting such controlled modulation can be employed.

In some embodiments, the output surface 146 can be represented by amathematical function as a combination of a base profile and amodulation profile. By way of illustration, the surface profile along across-sectional cut passing through the center of the surface (i.e., theintersection of an optical axis of the lens with the surface) along onedimension of the surface (herein denoted as the x-dimension) can bedefined as follows:

F(x)=f(x)+P(x)  Eq. (1),

wherein,

F(x) denotes the surface profile along the cross-sectional cut,

f(x) denotes a base profile, and

P(x) denotes a modulation profile.

P(x) is selected to be a function having a continuous first derivative.In other words, the first derivative of P(x), herein denoted as

$\frac{{P(x)}}{x}$

or P′(x), exhibits no discontinuity. Further, f(x) can be selected toexhibit a continuous first derivative.

A rotation of the above cross-sectional profile about an optical axis ofthe surface would generate a two-dimensional rotationally symmetricsurface profile. In other embodiments, the surface profile may not berotationally symmetric. For example, the cross-sectional profiles alongtwo orthogonal dimensions (e.g., x and y dimensions) can be different.By way of example, in the above example, the surface profile along across-sectional cut passing the center of the surface along anorthogonal dimension (the y-dimension) can be characterized by adifferent base profile and/or modulation profile.

A variety of functions can be employed for the base and the modulationprofiles defined above in Equation (1). By way of example, the surfacecan be rotationally symmetric with a semi-circular base profile and asinusoidal modulation profile along one dimension of the surface (whichcorresponds in two dimensions to a hemispherical base profile and anundulating surface having sinusoidal variations along each directionalong the surface). For example, the surface profile along one dimension(herein the x-dimension) can be defined as follows:

F(x)=√{square root over (R ² −x ²)}+∝ sin(β·x)  Eq. (2)

wherein R is a constant corresponding to the radius of the baseprofile), ∝ is a constant corresponding to an amplitude of thesinusoidal modulations, and β denotes the frequency of the sinusoidalmodulations. The cross-sectional profile defined by the above Equation(2) can be rotated about an optical axis of the surface to generate atwo-dimensional surface characterized by a hemispherical base profile onwhich a plurality of sinusoidal modulations are disposed. The amplitudeand the frequency of the sinusoidal modulations can be selected based ona desired modulation of the output beam. For example, for a givenamplitude of the modulations, increasing the modulation frequency canincrease the divergence angle of the beam, e.g., as characterized byfull width at half maximum (FWHM) of the light intensity distribution ina plane perpendicular to the direction of propagation. Further, changingthe amplitude of the modulations while keeping the frequency ofmodulations constant can also result in a change in the divergence angleof the output beam. In some cases, the amplitude and the modulationfrequency can be both changed so as to keep the divergence angle of thebeam constant while changing another characteristic of the beam, e.g.,its cross-sectional shape or its texture on a target surface.

In some embodiments, one type of surface modulation is employed over oneportion of the output surface 146 of the zoom lens 140 and another typeof surface modulation is employed over another portion of the surface ofthe lens 140. In this manner, the spread of the light exiting throughthe system via one portion of the output surface of the zoom lens 140can be different than the spread of the light exiting the system viaanother portion of that output surface. By way of example, FIG. 5B showsa top view of an embodiment of the output surface 146 of the zoom lens140 in which sinusoidal surface modulations with one frequency arepresent in a central region (CR) of the lens output surface 146 andsinusoidal surface modulations with a different frequency (e.g., a lowerfrequency) are present in a peripheral region (PR) of the lens outputsurface. In this embodiment, the portion of the light leaving the lensthrough the central portion of the lens can show a maximum angulardivergence that is different, e.g., greater, than a maximum angulardivergence exhibited by the light rays exiting the lens through theperipheral region of the surface.

In some embodiments, the frequency of the surface modulations can varycontinuously from the center of the output surface 146 of the zoom lens140 to an outer boundary of that output surface. Further, while in manyembodiments discussed herein, the surface modulations are disposed onthe output surface of the zoom lens, in some other embodiments, thesurface modulations can be disposed on the inner surface of the zoomlens or both the inner and outer surfaces.

As noted above, in some embodiments, the output surface of the lightpipe, e.g., the output surface 136 depicted in FIG. 1A, can be shaped soas to impart a desired cross-sectional shape to the light exiting thelight pipe. By way of example, FIG. 6A schematically depicts an outputsurface of the light pipe, which is shaped generally as a square withrounded corners. The rounded corners ensure that the emitted lightoutput, though generally square shaped, lacks sharp corners. As anotherexample, FIG. 6B schematically depicts another embodiment of an outputsurface of the light pipe, which has a hexagonal shape. In someimplementations of this embodiment, the light pipe can have a squarecross-section while its output surface has a hexagonal shape. Yet, inanother embodiment, the output surface of the light pipe can have anoctagonal shape. In some implementations of such an embodiment, thelight pipe can have a square or hexagonal cross-sectional shape whileits output surface has an octagonal shape. The octagonal shape of theoutput surface of the light pipe can impart a similar shape to thecross-sectional profile of the light beam exiting the light pipe. Theoctagonal shape of the light beam can be further adjusted viamodulations of the output surface of the zoom lens to provide an outputbeam that has an approximately round cross-sectional shape.

In some embodiments, a light interface unit is employed to facilitatecoupling of the light emitted by one or more light sources, e.g., one ormore LEDs, into the light pipe. By way of example, the light interfaceunit can include an input surface that conforms to an output surface ofa lighting unit in which the light sources are disposed, e.g., ahemispherical dome cover of an LED unit, to facilitate the delivery ofthe light emitted by the light sources to the light pipe. In someembodiments, the light interface unit can be formed integrally with theremainder of the light pipe, e.g., it can form a proximal portion of thelight pipe. In some embodiments, the light interface unit can not onlyfacilitate the coupling of the light emitted by the source into thelight pipe, but it can also provide some mixing of the light.

By way of example, FIG. 7 schematically depicts a light pipe 700according to such an embodiment, which includes a proximal portion 700 athat functions as a light interface unit for receiving light from alight source 110 and delivering the light to the remainder of the lightpipe 700 b. The light interface unit 700 a further provides some mixingof the light rays (see, e.g., exemplary light rays A and B) prior totheir delivery to the remainder of the light pipe. In this embodiment,the light interface unit includes a cavity 701 formed by a curved inputsurface 702 that terminates in an apex 703. The input surface 702receives the light from the light source 110 and couples the light intothe light interface unit 700. The input surface 702 is configured suchthat a substantial portion of the light incident thereon (e.g., at leastabout 80%, or at least about 90%, or 100%) is refracted to be redirectedtoward a peripheral surface 704. In this embodiment, the peripheralsurface is configured in a manner known in the art to cause totalinternal reflection of the light rays incident thereon, or at least thetotal internal reflection of a substantial portion of the incident lightrays (e.g., at least about 80% or 90% of the incident light rays), so asto redirect those rays toward the remainder portion 700 b of the lightpipe 700. In some other embodiments, the peripheral surface can bemetalized to cause specular reflection of the light rays incidentthereon. Although in this embodiment, the light interface unit is formedintegrally with the remainder of the light pipe, in other embodiments,it can be a stand-alone unit that is optically coupled to the lightpipe. In such cases, the light interface unit and the light pipe can becoupled to one another, e.g., by using an adhesive or seating the lightinterface unit and the light pipe in a holder in optical alignmentrelative to one another. By way of further illustration, the lightinterface unit 700 a can be formed similar to the lenses disclosed inU.S. Published Application No. 2010/0226127 entitled “Light MixingOptics and System,” which is herein incorporated by reference in itsentirety.

As another example, FIG. 8 schematically depicts a light pipe 800 thatincludes a concave light receiving surface 801, which provides a cavityin which a light source 802, herein an LED having a convex dome 802 a,can be seated. In this embodiment, the concave light receiving surface802 conforms substantially to the convex surface of the LED dome Thematching of these surfaces can advantageously allow efficient couplingof the light emitted by the LEDs into the light interface unit.

In some embodiments, different portions of the light pipe can exhibitdifferent cross-sectional shapes. For example, a portion of the lightpipe can have a circular cross-section while another portion of thelight pipe can have a square or a hexagonal cross-section. By way ofexample, the different cross-sectional shapes can be utilized tomodulate, e.g., enhance, coupling of the light into and out the lightpipe while ensuring effective mixing the light as it propagates alongthe length of the light pipe. By way of illustration, FIG. 9schematically depicts a light pipe 900 having a proximal portion 900 athat exhibits a circular cross-section, an intermediate portion 900 bthat exhibits a hexagonal cross-section, and a distal portion 900 c thatexhibits a square cross-section. The light is coupled into the lightpipe via an input surface 901 of the proximal portion and is coupled outof the light pipe via an output surface 902 of the distal portion 900 c.In this embodiment, the portions 900 a, 900 b, and 900 c are formed asan integral unit. In other embodiments, these portions can be formed asseparate units and then assembled in a manner known in the art. Further,the ordering of the cross-sectional shapes can be different than thosedepicts in FIG. 9. For example, in some embodiments, the distal portion900 c can have a circular cross-section to impart a circular shape tothe cross-section of the light beam exiting the light pipe.

In some embodiments, a holder employed in a system according to theteachings of the invention in which the light pipe is seated can includea plurality of legs for coupling to a plurality of openings in a printedcircuit board (PCB) on which a light source, e.g., an LED, is mounted.By way of example, FIGS. 10A and 10B show schematically an opticalsystem 1000 according to an embodiment of the invention that includes aholder 1001 in which the light pipe 130 is seated. The light pipe 130 isoptically coupled to a light source 110 for receiving light therefrom.Similar to the previous embodiments, the optical system 1000 furtherincludes a zoom lens 1004 that receives light from an output surface ofthe light pipe and projects the received light onto a target surface.The holder includes two legs 1005 and 1006 at its proximal end. The legs1005 and 1006 include, respectively, tips 1005 a and 1006 a that areconfigured for insertion into openings 1100 a and 1100 b of a PCB 1100,shown schematically in FIG. 10C. The legs advantageously allow opticalalignment of the light pipe 130 seated in the holder with the lightsource 110, e.g., an LED, disposed on the PCB 1100.

In some embodiments, the zoom lens in a system according to theinvention can include a baffle for preventing certain light rays exitingthe output surface of the light pipe, e.g., those light rays that missthe zoom lens, from reaching the external environment. For example,FIGS. 11A and 11B are partial schematic views of an embodiment accordingto the teachings of the invention in which the zoom lens 140 includes abaffle 141. As shown in FIG. 11A, when the zoom lens is moved away fromthe output surface 136 of the light pipe 130 to be at the distallocation, some of the light rays, e.g., the exemplary light ray A, thatleave the output surface of the light pipe at relatively largedivergence angles, are not incident on the lens, i.e., they miss thelens. The baffle captures these light rays and prevents them fromreaching the external environment. In some embodiments, an inner surface141 a of the baffle is black and/or is covered with light absorbingmaterial to absorb the light rays incident thereon, or at least asubstantial portion of those light rays. As shown in FIGS. 11A and 11B,as well as FIG. 10A, distal flange 123 of the holder 1001 is offsetrelative to the output surface 136 of the light pipe 130 (it is set backfrom the output surface) so as not to interfere with the baffle 141 asthe zoom lens is moved closer to the output surface, e.g., when the zoomlens is positioned at its proximal location. Such offset of the flangecan also be useful in certain embodiments in which the zoom lensincludes a concave surface facing the output surface of the light pipe,rather than a convex surface shown in the above embodiments, in that itcan provide room for the peripheral portions of the lens as the lens ismoved closer to the light pipe.

With reference now to FIG. 12, an exemplary lighting system 600 inaccord with various aspects of applicants' teachings is schematicallydepicted. As shown in FIG. 12, the lighting system 600 can comprisemultiple lighting modules 100 a-c, as generally described above withreference to FIGS. 1A-5B, and can be arranged such that their individualoutput light distributions substantially overlap on the target surface.In various embodiments, the lighting module 100 a-c can contain adifferent light source generating light of a different wavelength suchthat the lighting system 600 can be effective to mix different coloredlight in the combined output light distribution.

In some exemplary embodiments, each of the lighting modules 100 a-c canbe rotated slightly on its axis relative to one or more of the otherlighting modules 100 a-c. In embodiments in which the light pipes 130have a non-rotationally symmetric cross-section, rotation of one or moreof the lighting modules 100 a-c can be effective to change the totaloutput light distribution on the target surface, and reduce, forexample, the final appearance of the output light distribution having ashape corresponding to that of the cross-section of the light pipe.

By way of example, in some implementations, the lighting system 600 caninclude 30 light modules with the light pipes and/or the light sources(e.g., the LEDs) of the modules rotated about their longitudinal axes tovarying degrees relative to one another. For example, in some cases eachof the LEDs can be progressively rotated by 30 degrees (i.e., thirtypositions from 0 degree to 357 degrees).

Any of the lenses and or light pipes described above can be made ofpolymethyl methacrylate (PMMA), PMMI, glass, polycarbonate, cyclicolefin copolymer and cyclic olefin polymer, or any other suitablematerial. By way of example, the zoom lens can be formed by injectionmolding, by mechanically cutting a reflector or lens from a block ofsource material and/or polishing it, by forming a sheet of metal over aspinning mandrel, by pressing a sheet of metal between tooling dierepresenting the final surface geometry including any local facetdetail, and so on. Reflective surfaces can be created by a vacuummetallization process which deposits a reflective metallic (e.g.,aluminum) coating, by using highly reflective metal substrates viaspinning or forming processes. Faceting on reflective surfaces can becreated by injection molding, by mechanically cutting a reflector orlens from a block of source material and/or polishing it, by pressing asheet of metal between tooling die representing the final surfacegeometry including any local facet detail, and so on.

In some embodiments, the light pipe can be formed of silicone, which canprovide thermal resistance to the heat generated by the light source. Insome such embodiments, the light pipe made of silicone is seated withina holder such that the holder ensures that the light pipe would retainits shape even as its temperature rises due to heat generated by thelight source. In some such embodiments, the peripheral surface of thelight pipe is metalized and/or an inner surface of a holder in which thelight pipe is seated is metalized to provide specular reflection of thelight incident on the peripheral surface of the light pipe.

Any appended claims are incorporated by reference herein and areconsidered to represent part of the disclosure and detailed descriptionof this patent application. Moreover, it should be understood that thefeatures illustrated or described in connection with any exemplaryembodiment may be combined with the features of any other embodiments.Such modifications and variations are intended to be within the scope ofthe present patent application.

1-42. (canceled)
 43. An optical device, comprising: a light pipe havinga proximal end adapted for optical coupling to a light source to receivea plurality of light rays therefrom and a distal end providing an outputsurface for the light rays, said output surface comprising a pluralityof microlenses and surface texturing formed thereon, said light pipebeing configured to cause mixing of the light rays via reflection at oneor more lateral surfaces thereof as the light rays pass through thelight pipe, and a lens optically coupled to said output surface toreceive light therefrom.
 44. The optical device of claim 43, whereinsaid light pipe comprises an input surface at the proximal end forreceiving said light rays from the light source.
 45. The optical deviceof claim 44, wherein said output surface has a greater cross-sectionalarea than said input surface.
 46. The optical device of claim 43,wherein said lens comprises a zoom lens.
 47. The optical device of claim43, wherein said light pipe has a polygonal cross section.
 48. Theoptical device of claim 47, wherein said polygonal cross section isselected from the group consisting of a square, a rectangular, ahexagonal, and an octagonal cross section.
 49. The optical device ofclaim 44, wherein said lateral surfaces extend from said proximal end tosaid distal end.
 50. The optical device of claim 49, wherein any twoopposed lateral surfaces of said light pipe diverge in a direction fromsaid input surface to said output surface.
 51. The optical device ofclaim 49, wherein said lateral surfaces are configured to cause totalinternal reflection of at least some of the light rays incident thereon.52. The optical device of claim 43, further comprising a holderproviding a housing for said light pipe.
 53. The optical device of claim43, wherein said light source comprises an LED.
 54. The optical deviceof claim 43, wherein said light source comprises two LEDs providinglight at different colors.
 55. The optical device of claim 43, whereinsaid light pipe comprises at least two portions exhibiting differentcross-sectional shapes.
 56. The optical device of claim 44, wherein saidinput surface comprises a cavity for at least partially receiving thelight source.
 57. The optical device of claim 56, wherein said cavitycomprises a concave surface that matches a convex light-emitting surfaceof the light source.
 58. The optical device of claim 46, wherein thezoom lens comprises a lens providing a positive optical power andanother lens providing a negative optical power.
 59. An optical system,comprising a plurality of light modules disposed adjacent to oneanother, each of said light modules comprising: a light pipe forreceiving light from a light source at a proximal end thereof andguiding the received light at least partially via reflections at its oneor more peripheral surfaces to a distal end thereof providing an outputsurface through which light exits the light pipe, said light pipe havinga non-rotationally symmetric cross-section, and a lens for receiving atleast a portion of the light exiting the light pipe to form an outputbeam, wherein each of the light modules is rotated on its longitudinalaxis relative to one or more of the other light modules, and wherein thelight modules are positioned and oriented relative to one another suchthat an output beam of each light module at least partially overlapswith an output beam of at least another light module over a targetsurface so as to provide an illumination pattern on that surfacecharacterized by a light distribution exhibiting a reduced appearance ofthe cross-sectional shape of each of the light pipes and having across-sectional geometry different than a cross-sectional geometry ofeach of said light pipes.
 60. The optical system of claim 59, wherein atleast two of said light modules include light pipes having differentcross-sectional shapes.
 61. The optical system of claim 59, wherein saidlight modules are progressively rotated by a selected angle relative toone another.
 62. The optical system of claim 59, further comprising aplurality of microlenses coupled to the output surface of the light pipeof each of said light modules.
 63. The optical system of claim 59,wherein the light pipe of each of said light modules comprises an inputsurface at the proximal end for receiving said light rays from the lightsource.
 64. The optical system of claim 59, wherein the output surfaceof the light pipe of at least one of said light modules has a greatercross-sectional area than the input surface thereof.
 65. The opticalsystem of claim 59, wherein said lens of at least one of said lightmodules comprises a zoom lens.
 66. The optical system of claim 59,wherein said one or more peripheral surfaces are configured to causetotal internal reflection of light incident thereon.
 67. The opticalsystem of claim 59, wherein the light pipe of at least one of said lightmodules comprises at least two portions exhibiting differentcross-sectional shapes.
 68. The optical system of claim 59, wherein saidnon-rotationally symmetric cross-section is selected from the groupconsisting of a square, a rectangular, a hexagonal and an octagonalcross-section.